A printer, a facsimile machine, a copying machine, a plotter, and a Multi-Function Peripheral (MFP) which combines the functions of two or more of such equipments, may have a recording head which is configured to form an image on a recording medium which is transported, by jetting ink on the recording medium. The recording medium may be formed by any suitable material or member capable of bearing the image thereon. Examples of the recording medium include a transfer member, recording paper, recording sheet and the like. In this specification, “forming the image on the recording medium” refers to any suitable means of making the image on the recording medium, including recording, printing, plotting, transferring and the like.
In this specification, the “image forming apparatus” refers to any apparatus capable of forming the image on the recording medium which may be made of a material such as paper, yarn, fiber, silk screen or cloth, leather, metal, plastic, glass, wood and ceramic, by jetting ink on the recording medium. In addition, in this specification, “image formation” refers not only to forming of the image, such as characters and graphics, having a meaning, but also to forming of the image, such as patterns, having no meaning (that is, simply jetting the ink). Furthermore, in this specification, the “ink” not only refers to the ink in the narrow sense, and also refers to any liquid, such as DNA samples, resists and pattern materials, that may be jetted onto the recording medium.
In the ink-jet type image forming apparatus, the image formation is made by jetting the ink, which includes a coloring material, in the form of ink drops (or droplets). For this reason, in conveniences such as the feathering in which the dots formed by the ink drops are distorted in a whisker shape, and the color bleeding in which the colors of the adjacent ink drops of different colors formed on the recording medium mix with each other to thereby make the color boundary unclear, may occur. Moreover, it takes time for the ink drops formed on the recording medium to dry after the image formation.
A Japanese Laid-Open Patent Application No. 8-323977 proposes a method of preventing the spreading by using a heater before or after the image formation, in order to promote drying of the ink after the image formation.
A Japanese Laid-Open Patent Application No. 2002-137378 proposes coating a pretreating liquid which reacts with the ink and promotes prevention of the spreading from a coat roller onto the recording medium. A Japanese Laid-Open Patent Application No. 2005-138502 proposes spraying a pretreating liquid in the form of mist from an ink-jet head onto the recording medium.
However, the power consumption of the image forming apparatus increases when the heater is used as proposed in the Japanese Laid-Open Patent Application No. 8-323977. On the other hand, when the pretreating liquid is coated by use of the coat roller or the ink-jet head as proposed in the Japanese Laid-Open Patent Applications No. 2002-137378 and No. 2005-138502, the pretreating liquid may not be coated uniformly on the recording medium. In addition, because the pretreating liquid is in liquid form, it may take time for the pretreating liquid to dry after reacting with the ink on the recording medium. Consequently, the recording medium may curl or shrink, to thereby increase the possibility of a paper jam occurring in the image forming apparatus. Furthermore, when the ink-jet head is used to coat the pretreating liquid as proposed in the Japanese Laid-Open Patent Application No. 2005-138502, the cost of the image forming apparatus increases because of the need to employ a combination of the pretreating liquid and the ink-jet head that would not easily cause a nozzle of the ink-jet head to clog, and such a combination is limited.